Dental casting apparatus



H. R. BERGERl l 2,209,381

DENTAL CASTING APARATUS y Filed Dec. sq, 1937 s-sneetS-sxyeet-z July 3o, 1940.

INV'VENTOR Herbert erg A .A w

@A@ is mm1. JM H .BY v

2A;TORNEY I* AJuly so, 1940. HRQERG-m x zzoaasl DENTAL CASTING", APPARATUS Filed Deo, 30, 19:57* "3 sneetgsheeys n AMML'TER NAIN INVENTOR ATTORNEY K Patented July 30, 1940 UNITED STATE DENTAL CASTING APPARATUS.

Herbert R. Berger, J. F. Jelenko &

lApplication Decenib 2 Claims.

Brooklyn. N. Y., assig/'nor to Oo., Inc., New York, N. Y.

er 3o, 1937, serial Nn. 182,600 (c1. ca -sal)- This invention relates to improvements in casting apparatus of the type capable of use in dental and jewelry work.

In the casting of metals for dental work, jewelry, or other ne work, the metal is usually heat-Vv ed until the operator decides by visual inspection that the 'proper condition yhas been reached, at which time the metal is forced into the mold, as

by centrifugal action. Many of the castings thus l0 formed are defective and must be discarded, and uniformity of the castings is impossible to obtain by this method. The presence of oxide spots, blowholes, and porous portions in the castings render them unfit for many uses, and the porous conditions usually presen-t not only retains dirt but prevents the metal from taking a high polish. An important object of the present invention is the provision of .a casting apparatus which can be operated to produce castings'of a uniform` character and high quality.

Another object of the invention is to provide a casting apparatus which is of simple construction, which melts the metal electrically and which is simple in operation. f I A further object' of the invention is te provision of apparatus of this character which may be easily applied, to centrifugal casting Imachines now in use.

Other objects and advantages of the invention will be apparent during the course of the following description.

In the accompanying drawings, which form ya part of ,this specification and wherein like charact-ers of reference denote like parts throughout,

Figure 1 an elevation of a casting apparatus embodying the present invention, parts being shown in section, v

Figure 2 is an elevation at a right angle to Figure 1, Y l Figure 3 is a detail sectional view of the contact rod and its supporting mechanism, taken on line 3-3 of Figure'l,

Figure 4 is a top plan view of the apparatus, Figure 5 is a longitudinal sec-tional View through the heating chamber,

Figure 6 is a side elevation thereof,

Figure '7 is a transversesection thereof, on line 'I--l ofFigure 5, f 1, Figure `8 is an edge elevation of ythe heating chamber closure,

Figure 9 is a longitudinal sectional view of the removable cruci'ble, f

Figure 10 is anend elevation thereof. y Figure 11 is a diagram of the electricalY circuits employed,

Figure 12 is a detail elevation of `a modiiied form'of detachable contact mechanism, and, f Figure 13 is a perspective detail view of a further modification of the contact mechanism.

In the drawings, wherein for the purpose of il- 5 lustration is shown a preferred embodiment of the invention, the numeral I2 designates the casing of a centrifugal vcasting machine which encloses asuitable p'wermechanism such as a spring motor which drives avertical shaft I3 10 arranged .centrally of the casing. `A horizontal bar Il is secured to shaft I3 ata point above the top of casing vI2 and is adapted to rotate with shaft I3. A mold and furnace supporting `bar I5 is normally disposed ata right angle to the bar 15 it and is pivotally connected to one end thereof by means of -a bolt or other connection. A counterweight i6 is adjustably supported on the opposite end of bar I4 lby means of a set screw" I1 or the like. y 20 A mold supporting cradle I8 is secured to the end of arm I5 farthest from arm i4 and 'supportsi a removable flask or mold I9. A furnace or oven 291s ad'justably secured to the arm i5 adjacent the cradle I8 by means of a bolt 2I lattached to `25 the mold and extending through a slot 22 in the arm i5. A wing-nut 23 secures the furnace in position on arm I5. Suitable projections 24 on `tire yuncler side'o'f furnace 20 engage the sides of arm I5 to center the furnace. 30 l A vertically movable rod 25 is slidably secured to casing i2 and has an enlarged upper end adapted to rest upon the upper edge of 'bar I4. When the spring motor is wound, rod 25 is moved up into engagement'with bar I4, as seen in Figure 35 4, and prevents movement of the bar. When it is desired to release bar i4, the bar is movedl away from rod 25 `against the tension of the spring motor, permitting rod 25 to drop out of the path of bar I4; which is then'released ,andv 40 allowed to spin. When bar I4 spins, lbar I5 swings into longitudinal alignment therewith, and the molten metal in furnace-20 is forced into mold I9 by centrifugal action. The construction thus far described lis of the usual construction. 4

in accordance with the present invention, the furnace' 20 comprises a refractory muiiie 26 spaced a substantial distance lfrom the inner walls of the furnace casing and embedded inthe end walls thereof. Electric resistance windings 50 21 encircle the outer periphery of muiiie 26 and are covered by a layer of some suitable insulating material such as alundum cement 28 of substantial thickness. Suitable heat resistant material such as asbestosv fiber 29 is packed between 55 the layer 28 and the furnace casing, which may be of metal or other suitable material. The insulation prevents heat losses.

A thermocuple 30 is disposed in the muiile 26 and is connected Iby suitable wiring to the two central contacts 3| on a, contact panel 32 secured to one side of the furnace casing. End contacts 33 on vboard 32 are connected to the resistance elements 21. In Figures 2, 6, 7 and 11 the contacts 3| and 33 are shown as arranged in a horizontal row on panel32, projecting laterally from the panel and the furnace in a. horizontal direction. The contacts 3| and 33 have horizontal bores, as indicated byY dotted lines, extending of depending side bars or legs 35 which rest upon the base of casing I2, as seen in Figures l and 2. 'Ihe band 34 is split and has its endsturned out to form flanges 36 between which a plate 31 is secured by bolts 39. A vertical sleeve 39 is hingedly connected to the outer end of plate 31 by means of a vertically arranged pintle 40 which permits movement of sleeve 39 about a'vertical axis.

`A cylindrical rod 4| is loosely arranged in sleeve 39 to slide vertically therein and is secured at its tcp to a horizontal contactv plate 42. Contact elements 43 extend vertically from plate 42 and are turned over at their ends to form horizontal extensions to be received in the bores of contacts 3| and 33. A flexible conduct-or 44 carries wires which are connected to contact elements 43 to carry electric current thereto. By reference to Figure 4 it will be seen that contacts 3| and 33 are staggered inlength and that when arm I4 is movedto release rod 25, the contacts 3| and 33 will be pulled from engagement with contact elements 43, permitting rod 4I to drop in sleeve 39 and allowing arms 4I4 and |5 to be rotated by the motor in casing I2 without interference from rod 4I or contact plate 42.

By reference to Figure it will be seen that the front end of the furnace casing is provided with a circular opening 45 which coincides with the inner periphery of the muiiie 26. A smaller opening 481s arranged in the rear wall of the Y 41 removed from the furnace.

furnace casing concentrically with the muiiie and i is arranged inalignment with the gate of mold 9. In Figures 9 and l0 is shown the crucible This crucible is cylindrical in shape and is adapted to be snugly received within the muiile 25. The'sprue 49 on .the rear of the crucible extends through opening 46 to the gate of the mold I9. A dam' 50 closes the lower half of the front end of the crucible,

and a removable door 49 ts in opening45 to close the muiiie when the crucible is in place. The parts are held firmly in place by centrifugal force when the arm I4 is spun.

The crucible 41 may be made of any suitable material. For use `.with some metals, a refractory crucible can be employed, but for melting gold and other precious metals, a carboncrucible should be used to produce a reducing atmosphere and to prevent sticking of the metal to the walls of the crucible. The inner walls of the crucible taper at their ends to the opening in sprue 48. The dam 53 may be of any suitable material, such asalundum. v

In Figure 11 is shown a diagram of the circuits connecting contacts 3| and 33 tothe pyrometer 5I and current control device 5.2. Wires.

53 connect the thermocouple contacts 3| with pyrometer 5I so that the temperature in the furnace can be read at 52. The variableresistance, rheostat or other control device 52 is arranged in circuit 54 with the furnace resistance contacts 33, and an ammeter 55 is included in this circuit. 'l

In operation, the metal is heated in crucible 41 until the desired temperature has been reached, indicated on pyrometer 5I. The -arm I4 is then 'pulled back to release rod 25 and contactelements 43, and then released to be spun by the mlotor in casing I2. The molten metal is passed into the mold by centrifugal force and the casting is formed while the mold is spinning, in the usual manner. By the use of the thermocouple 30 and pyrometer 5|, guesswork or visual inspection is not relied upon to determine the time for molding the metal. By experiment. the exact temperature for a givenl amount of a given metal may be determined, and the arm I4 may then be released when the previously determined temperature has been reached. In this way, castings of a uniform fine character and grain structure may be obtained from each molding operation Tables may be prepared for the guidance of the furnace operator. k

By reason of the slot 22 in arm I5, the position of the furnace may be adjusted to accommo- .date molds of various sizes. 'The hinge 40 permits movement o fv rod 4I to align the contact elements 43 with the openings in the furnace contacts 3| and 33. Because of the staggered lengths of the furnacel contacts 3| and 33 there will be no possibility of engaging the contactelements 43 lwith the wrong furnace-contact.

In place of the arrangement 'of contacts shown in Figures 1, 2, 4, 6 and 7, the construction shown in Figure 12 may be employed in which the contacts 3|' and 33 are disposed ina vertical row. and contact plate 42' is vertically disposed. The contacts 3|' and.33 are imperforate and contacts 43 are in the form of horizontally arranged spring clips which engage the furnace contacts. Movement of the arm I4 to release rod 25 will disengage contacts 43', 3|" and 33' and will permit rod 4|`to drop out ofthe path of arm I4.

In Figure 13 the outer contacts 43 are carried bya yoke 42 which is mounted on the top of tubular sliding rod 4|'. The two center contacts 43 are carried by a central support 42b carried by a rod 4| of substantially less diameter than tubular rod 4I' in which it is telescopically received. As the two pairs of contacts are independently supported and manipulated a much better contact engagement is obtained.

Any other suitable detachable contact construction may obviously be employed. If desired, the rod 25 may be omitted and the rod 4I and contact plate 43 relied upon to hold the arm I4 in a stationary position, in which case the rod ,4| and plate 42 become the stop means.

Any suitable motive power for shaft I3 may be used. It will be seen that the band'34 and associated contact structure may be readily applied to casting apparatus now in use, and the furnace 20 readily substituted for the usual crucible and holder used with a blow torch in standard casting apparatus. By the use of this invention consistently uniform castings of fine quality may be obtained with ease by following a prepared chart or table, and any casting may be easily duplicated by following the-instruments 5I and 55 in place of thel usual procedure of visually inspect.

ing the metal to determine the time for casting.

While I have shown and described the pre- `fe'rred embodiment of the invention, it is to be v understood that various changes in the size, shape y and arrangement of parts may be resorted to without departing from the spirit of the invention or the scope of the subjoined claims.

Having thus described my invention, what I claim anddesire to protect by Letters Patent is:

1. In a centrifugal casting machine, a casing, a rotatable shaft extending vertically from the casing, an arm mounted on the shaft and rotatable therewith, a heating chamber djustably mounted on said arm at a point spaced from the shaft, a mold carried by the arm adjacent the heating chamber, an electric heating element in the heating chamber, a thermocouple in the heating chamber, contacts carried by the heating chamer exteriorly thereof and connected to the heating chamber and thermocouple, a vertically. disposed sleeve pivotally supported by said casing, a vertically movable member slidably engaging said sleeve, contacts carried by the vertically movable member and detachably engaging the heating chamber contacts, said .contacts being disengaged when the arm is moved-in one direction to permit the vertically movable member to drop out of the path ,of the arm, motive means in said casing to rotate the arm-in the opposite direction, and electrical circuits connected to the contacts on the vertically movable member.

2. In a centrifugal casting machine, a casing, a rotatable shaft extending vertically from the casing, an arm mounted on the shaft and rotatable therewith, ay furnace mounted von said arm at a point spaced from the shaft, am'oid carried by the arm adjacent the furnace,y an electric heating element in the furnace; a thermocouple in the furnace, contacts arranged on the exterior of the furnace and connected to the heating element and thermocouple, a split band secured to the casing adjacent the upper end thereof, a

vertically disposed sleeve pivotally supported by the opposite direction, and electrical circuits connected to the -contacts on the vertically movable member.

I-ERBERT R. BERGER. 

